docs: def trapezoidIntegration(self, x, y):
          """Perform trapezoid integration.
  
          Parameters
          ----------
          x : array_like
              Wavelength set.
  
          y : array_like
              Integrand. For example, throughput or throughput
              multiplied by wavelength.
  
          Returns
          -------
          sum : float
              Integrated sum.
  
          """
          npoints = x.size
          if npoints > 0:
              indices = N.arange(npoints)[:-1]
              deltas = x[indices+1] - x[indices]
              integrand = 0.5*(y[indices+1] + y[indices])*deltas
              sum = integrand.sum()
              if x[-1] < x[0]:
                  sum *= -1.0
              return sum
          else:
              return 0.0